Impact of the selenisation temperature on the structural and optical properties of CZTSe absorbers

• Published in: Solar energy materials and solar cells 2016-08, Vol.152, p.42-50
• Main Authors: Márquez-Prieto, J., Yakushev, M.V., Forbes, I., Krustok, J., Edwards, P.R., Zhivulko, V.D., Borodavchenko, O.M., Mudryi, A.V., Dimitrievska, M., Izquerdo-Roca, V., Pearsall, N.M., Martin, R.W.
• Format: Article
• Language: English
• Subjects: Cu2ZnSnSe4; Diffraction; Emission analysis; Excitation; Glass; Optical spectroscopy; Photoluminescence; Photonic band gaps; Photovoltaic cells; Selenisation; Solar cells; Structure
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2016.03.018

We present structural and optical spectroscopy studies of thin films of Cu2ZnSnSe4 (CZTSe) with strong copper deficiency deposited on Mo/Glass substrates and selenised at 450, 500 or 550°C. Solar cells fabricated from these films demonstrated efficiencies up to 7.4% for selenisation at 500°C. Structural analysis based on X-ray diffraction and Raman spectroscopy revealed the presence of SnSe2 in the film selenised at 450°C but not in the films selenised at higher temperatures. A progressive decrease of the Sn and Se content was observed as the selenisation temperature increased. Photoluminescence excitation was used to determine the bandgaps at 4.2K. Detailed measurements of the temperature and excitation intensity dependencies of the photoluminescence spectra allow the recombination mechanisms of the observed emission bands to be identified as band-to-impurity and band-to-band transitions, and their evolution with selenisation temperature changes to be analysed. The strongest band-to-band transition is recorded in the PL spectra of the film selenised at 500°C and can be observed from 6K to room temperature. The compositional and structural changes in the films and their influence on the optoelectronic properties of CZTSe and solar cells are discussed. •CZTSe thin films on Mo/glass substrates deposited by selenisation of metal precursors.•Changes of elemental composition and structure with selenisation temperature measured.•PL temperature and excitation intensity dependence analysed, PL bands identified as band-to-impurity and band-to-band transitions.•The band gaps using PLE determined.•Solar cell performance with optical spectroscopy parameters correlated.